In general, the invention relates to damper assemblies for use in vehicle suspension systems, and more particularly, to a monotube strut and base cup assembly.
Current vehicle suspensions frequently incorporate strut assemblies as both a damping device and, in some applications, part of the suspension""s load bearing structure. Monotube struts or dampers are conventionally known which include a piston with a connected piston rod. The piston is slidably contained in a fluid filled tube or chamber.
Typically, in prior designs, an end of the piston rod opposite the piston is held in a hole formed through a base cup of the strut by a threaded nut on a side of the cup outside the fluid chamber. Typically, an opposing nut is fastened to the piston rod on an opposite side of the base cup in order to provide an anti-rotation feature for the piston rod that allows the connection to be tightened. This conventional design requires a relatively thin base cup in order to minimize dead length for the design. However, a thin cup increases the chances of fatigue failure of the cup by permitting the cup and associated members to deflect in response to loads from the strut.
Controlled dampers require an electrical connection to be made with the piston rod. Typically, the connector includes a terminal portion inserted into the piston rod and a ground portion in contact with the strut. The piston rod can be provided with sensors that sense the relative position between the sprung and unsprung masses (body and wheel assembly) of a vehicle. Another example discloses electrical components extending into the rod to control the magnetic flux in the damper to effect changes in a MR fluid and thus, effects damping characteristics of the damper unit. These electrically controlled dampers had been provided with an electrical connection to the rod, introducing a potential electrical failure point between the electrical connector and the nut. The electrical connector cannot be made integral with the nut because the connector needs to be oriented whereas the nut can tighten at any angular position. Finally, the prior art dampers have retained the connector within the cup assembly and a cap has been press fit to the cup for that purpose. However, the cap can be dislodged when the relatively thin base cup deflects under heavy damping loads.
It is an object of the present invention to provide a strut assembly that overcomes these disadvantages.
One aspect of the present invention provides a vehicle suspension damper assembly configured to be arranged between a wheel assembly and a body of a vehicle the vehicle suspension damper assembly including a cup member with a threaded opening formed therein. A piston rod is provided, which includes a threaded portion, the threaded portion of the piston engaged in the threaded opening of the cup. An electrical connector is provided that includes a terminal portion received in an opening formed in the piston rod. The threaded engagement between the cup member and piston rod is a predetermined length that reduces deflection of the cup member to reduce transfer of load to the terminal portion of the electrical connector.
Other aspects of the present invention provide a cup member, which includes a first portion adapted to be fitted to a reservoir tube. The threaded opening of the cup member can be formed in the first portion. The cup member can include a second portion having a first seat formed therein for receiving the electrical connector. The cup member can include a slot formed in the second portion to allow the electrical connector to extend therethrough. A socket portion of the electrical connector can extend through the slot in the second portion of the cup member. The cup member can include a second seat adjacent the first seat for receiving a cap, and wherein the cap when fitted to the second seat, retains the electrical connector to the cup member.
The assembly can further include an electrical connector including a concave portion. The cap can include a convex portion, the concave portion being in contact with the convex portion of the electrical connector when the electrical connector and cap are assembled to the cup member. A ground terminal of the electrical connector can be provided to contact the cup member.
A ring member can be provided, the ring member being disposed between the piston rod and cup member. The ring member can contact a shoulder formed about the piston rod and a groove formed in the cup member.
The piston rod includes a bore extending in the axial direction. The rod can include a first countersunk portion of the axial bore for receiving the terminal portion of the electrical connector. The rod can include a second countersunk portion relatively distally formed with respect to the first countersunk portion, the second countersunk portion including a driving feature.
Another aspect of the present invention provides a method of assembling a vehicle suspension damper assembly. The method includes fitting a cup member into a reservoir tube of the damper, threading a piston rod into the cup member a predetermined distance, positioning an electrical connector into the cup member, forming an electrical connection between the electrical connector and a component within the piston rod and securing a cap in the cup member to encapsulate the electrical connector in the cup member. The method can further include threading the piston rod into the cup member includes engaging a driving feature of the piston rod with a driving device and rotating the piston rod. The method can further include contacting a stop feature of the piston rod to the cup member.
Another aspect of the present invention provides a vehicle suspension damper assembly including a means for fitting a cup member into a reservoir tube of the damper, means for threading a piston rod into the cup member a predetermined distance, means for positioning an electrical connector into the cup member, means for forming an electrical connection between the electrical connector and a component within the piston rod and means for securing the electrical connector in the cup member. The vehicle suspension damper assembly can further include means to stop the threading of the piston rod into the cup member.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.